It is known to position a co-axial counter-flow heat exchanger between a compressor and condenser in a refrigeration system to recover the waste heat produced during the refrigeration cycle. A significant problem associated with the use of such a heat exchanger is the detection and control of a leak which may possibly occur between the concentrically tubular passageways extending through the heat exchanger. If leaks are not detected and controlled, disastrous consequences may result. For example, in a super-market the loss of refrigerant gas from the primary refrigeration system resulting from a leak in the heat exchanger could result in the spoilage of perishable foods. Likewise, in a hospital where purified water is required, the leaking refrigerant gas could contaminate the water flowing through the heat exchanger.
U.S. Pat. No. 3,400,753, issued Sept. 10, 1968, attempts to control leaks through a heat exchanger by sensing the change in either the flow rate or the pressure differential between the two flow conduits (Page 2, lines 13-20). U.S. Pat. No. 3,400,753 reduces the flow rate in one of the conduits until the pre-set differential is again achieved. At this point the flow rate is allowed to increase. This system is much more complex than applicant's apparatus in requiring at least two flow rate controllers and a differential pressure-sensing means in addition to the necessary valves. Applicant's apparatus can be further distinguished from U.S. Pat. No. 3,400,753 for two reasons. First of all, applicant's sensing apparatus detects a change in parameter of only one fluid flowing through said heat exchanger. Therefore, there is no need for any comparison equipment. Secondly, applicant's apparatus positively interrupts flow through the heat exchanger until the leak can be eliminated and the apparatus is manually reset. U.S. Pat. No. 3,400,753 will allow fluid to flow through reboiler 4 once the pre-set differential is reached whether or not the leak has been eliminated.